One of the main causes of the stain of a toilet is the deposition of uric stone. The process by which the uric stone deposits is considered to be as follows: when urea contained in urine is decomposed by urease, an enzyme carried by bacteria, ammonia is generated, whereby the pH of a mixed drain consisting of urea and flush water increases; as the pH increases, the solubility of calcium phosphate which is produced by the reaction of calcium ions and phosphate ions contained in the urine decreases, and calcium phosphate together with organic components precipitates on such a place as the inner surface of the toilet. This is the "uric stone".
Accordingly, some methods are conventionally used wherein the pH of the mixed drain is kept low enough to impede the precipitation of calcium phosphate.
For example, the Japanese Published Examined Patent Application No. H5-57312 discloses a method wherein the pH of the urine, or a mixed drain composed of urine and flush water, is kept between 5 and 7.5 by adding acid substances.
The conventional method using acid substances, however, is not a satisfactory countermeasure to a stench since it cannot suppress the generation of ammonia adequately.
Besides, the method is accompanied by the problem that the downstream pipe of the toilet may corrode.
Furthermore, the maintenance work for supplying an acid substance is necessary and the supplying work may be sometimes dangerous.
The present invention is accomplished in view of the above problems, the main object of which is to provide a method of cleansing a toilet by which the formation of the stain of the toilet is effectively prevented and the generation of ammonia is suppressed adequately so that the stench can be prevented sufficiently.
Further, the present invention provides a system for cleansing a toilet which requires less maintenance work and is safer to users than the conventional method using acid substances.